This application is based on Japanese Patent Application No. 11-236782 (1999) filed Aug. 24, 1999, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a liquid container capable of maintaining a supply ability of ink, a liquid ejection mechanism employing the liquid container and a liquid ejection apparatus.
It should be noted that the present invention is applicable not only for a typical printing apparatus but also for a copy machine, a facsimile having a communication system, a wordprocessor having a printing portion, and so on, and further for an industrial printing apparatus composed with various processing systems.
2. Description of the Related Art
In general, a liquid container serving as an ink tank in a printing apparatus to be used in a field of an ink jet apparatus, is provided with a construction for adjusting a holding force of ink stored in the ink tank in order to satisfactorily perform ink supply for a printing head for ejecting the ink. This holding force is referred to as negative pressure since a pressure of an ink ejecting portion of the printing head becomes negative relative to an atmospheric pressure. (Such a member for generating the negative pressure will be hereinafter referred to as a negative pressure generating member.)
One of the easiest method for generating such negative pressure is to provide an ink absorbing body, such as a porous body including a urethane foam, felt and the like, within the ink tank to utilize capillary phenomenon (ink absorbing force) of the ink absorbing body.
For example, Japanese Patent Application Laid-open No. 6-15839 (1994) discloses a construction with choking up a plurality of ink absorbing bodies having mutually different density in the order of a high density absorbing body and a low density absorbing body toward a supply passage, over the entire tank, within the ink tank. The high density absorbing body has a longer total length of fiber per unit volume to have higher ink absorption capability, an d the low density absorbing body has a shorter total length of fiber per unit volume to have lower ink absorption capability. Joints between fibers are fitted under pressure so as to prevent interruption of ink due to admixing of air.
On the other hand, commonly owned Japanese Patent Application Laid-open Nos. 7-125232 (1995) and 6-40043 (1994) have proposed an ink tank having a liquid containing chamber which can increase an ink storage capacity per unit volume of the ink tank while the ink absorbing body is used and can realize stable ink supply.
In FIGS. 14A and 14B, shown are structural cross sections of the ink tank using the construction set forth above. As shown, ink tank 10 defines two spaces separated by a partition wall 13 serving as a separator wall provided with a communicating portion 20, such as a communication hole. One space is a liquid containing chamber 12 being enclosed except for the communicating portion 20 of the partition wall 13 and directly holding ink. The other space forms a negative pressure generating member containing chamber 11 housing a negative pressure generating member 30. In a wall surface forming the negative pressure generating member containing chamber 11, an atmosphere communicating portion 14, such as an atmosphere communication hole, for introducing atmospheric air into the container according to consumption of the ink, and a supply opening 16 having a pressure contact body 15 serving as ink leading member to a recording head not shown, are formed.
In FIG. 14A, a region where the negative pressure generating member holds the ink is shown by black dotted portion. On the other hand, the ink stored in the space is shown by cross-hatched portion. In order to prevent introduction of atmospheric air into the liquid containing chamber 12 through portions other than the atmosphere communication portion 14, the negative pressure generating member 30 is required to be tightly fitted onto the inner peripheral wall of the negative pressure generating member containing chamber 11.
Such ink tank achieving both of compact sizing and a high usage efficiency has been marketed by the assignee of the present invention and has been practically used. In the example shown in FIG. 14A, the pressure contact body 15 having a higher capillary force and a higher physical strength than the negative pressure generating member 30, is provided in the supply opening 16. The pressure contact body 15 is in contact with the negative pressure generating member 30 under pressure. In the vicinity of the communicating portion 20 between the negative pressure generating body containing chamber 11 and the liquid containing chamber 12, an atmospheric air introduction groove 21 is provided in order to promote introduction of the atmospheric air into the liquid containing chamber 12. In the vicinity of the atmosphere communicating portion, a space where no negative pressure generating member is present, namely a buffer chamber 18 is defined by means of a rib 17.
However, the construction set forth above is premised on that a urethane foam is used as the negative pressure generating member. If the negative pressure generating member formed of fiber with maintaining the same shape, density distribution of the negative pressure generating member can be differentiated due to difference of elasticity and hardness thereof.
In certain density distribution, stable gas/liquid exchange can be disturbed to possibly cause failure of ink supply in spite of the fact that the ink is remained in the ink tank.
Therefore, the inventors have made an extensive study for the density distribution in the vicinity of the atmospheric air introduction groove. As a result, it has been found the following problems.
Namely, as shown in FIG. 15A, when the negative pressure generating member 30 in the peripheral portion 50 of the atmospheric air introducing groove 21 has higher density than that of other portion, a capillary force to be generated becomes higher so that the ink can be held in the vicinity of the negative pressure generating member 30 being in contact with the atmospheric air introducing groove 21 even when the ink is consumed so as not to be introduced into the communicating portion 20. As a result, gas/liquid exchange is not initiated (FIG. 15B) or even if initiated, since the strength of the negative pressure upon gas/liquid exchange is determined by the portion 50 contacting with the atmospheric air introducing groove 21 of the negative pressure generating member 30, negative pressure becomes strong. Then, most of the ink in the negative pressure generating member 30 can be consumed out before all of the ink within the liquid containing chamber 12 is consumed, resulting in interrupting an ink passage from the liquid containing chamber 12 to the ink supply opening 15. It has been found that once the ink passage is interrupted, failure of ink supply can be caused.
The conventional atmospheric air introduction groove is formed into a buffer structure by providing a groove in a portion recessed in the partition wall. The density of the portion of the negative pressure generating member 30 in contact with the grooved portion is designed to be higher than the density of the portion in contact with the partition wall. In the case of the negative pressure generating member formed with a urethane foam, since the urethane foam has an appropriate elasticity, even when the urethane foam of the size greater than the volume of the negative pressure generating member containing chamber 11 is inserted thereinto to enhance tight contact with side walls, the urethane foam is compressed relatively uniformly so as not to cause substantial difference of density distribution.
However, the negative pressure generating member formed of fiber has low elasticity, particularly has little elasticity in the longitudinal direction of the fiber. Therefore, it has been found that density of the negative pressure generating member is increased in the portion contacting with the atmospheric air introducing groove by pressure contact of the negative pressure generating member to the partition wall.
It may eliminate increasing of the density of the portion 50 in the vicinity of the atmospheric air introducing groove by employing a structure advanced from the conventional buffer structure. However, it is possible that a large gap is formed in the buffer structure portion 51 due to tolerance of dimension of the negative pressure generating member 30 in a direction perpendicular to the partition wall 13.
If such a large gap is formed in the atmospheric air introducing portion 50, bubbles in the atmospheric air introducing portion 50 separated from the negative pressure generating member 30 can be aggregated in the gap to form a large bubble 52. The large bubble 52 can interfere flow of the air from the negative pressure generating member 30 to the liquid containing chamber 12. As a result, failure of ink supply can be caused.
On the other hand, when the negative pressure generating member 30 is inserted into the chamber 11 from the above, the negative pressure generating member 30 is expanded in greater extent at the buffer structure portion to cause difficulty in assuring tight contact with the bottom surface of the chamber 11.
The foregoing problem has not raise significant problem in the case of the ink tank employing the conventional urethane foam since difference of density distribution is hardly caused.
Accordingly, it is an object of the present invention to provide a liquid container, a liquid ejecting mechanism and a liquid ejection apparatus which can solve the problems set forth above with employing a negative pressure absorbing body formed with fiber and assure stable ink supply performance.
In the first aspect of the present invention, there is provided a liquid container comprising:
a negative pressure generating member containing chamber receiving a negative pressure generating member formed with a fibrous material and having a liquid supply portion and an atmosphere communicating portion;
a liquid containing chamber forming a substantially enclosed space having a communicating portion communicating with the negative pressure generating member containing chamber and storing a liquid to be supplied to the negative pressure generating member;
a partition wall separating the negative pressure generating member containing chamber and the liquid containing chamber and formed with the communicating portion;
an atmospheric air introducing mechanism in the form of a recess provided in the partition wall on the side of the negative pressure generating member containing chamber, in communication with the communicating portion; and
a projecting portion, provided in a part of the atmospheric air introducing mechanism, projecting on the side of the negative pressure generating member containing chamber.
The atmospheric air introducing mechanism may have a recessed portion buffering pressure contact of the negative pressure generating member onto the partition wall and a projecting portion improving workability in assembling the negative pressure generating member.
The atmospheric air introducing mechanism may include a plurality of vertically extending grooves through the recessed portion and the projecting portion.
The projecting portion may be provided at a lower portion of the atmospheric air introducing mechanism.
The projecting portion may be lower than a wall surface of the partition wall on the side of the negative pressure generating member containing chamber.
The communicating portion of the partition wall may be partly chamfered on the side of the negative pressure generating member containing chamber.
A part of the atmospheric pressure introducing mechanism may be tube-shaped.
The negative pressure generating member formed with fibrous material may be formed by stacking fibrous bodies with substantially the same directionality, and a direction of fiber may intersect with the partition wall.
The fibrous material may be olefin type resin fiber.
In the second aspect of the present invention, there is provided a liquid ejecting mechanism comprising:
a liquid container including:
a negative pressure generating member containing chamber housing a negative pressure generating member formed with fibrous material and having a liquid supply portion and an atmosphere communicating portion;
a liquid containing chamber forming a substantially enclosed space with a communicating portion communicated with the negative pressure generating member containing chamber and storing a liquid to be supplied to the negative pressure generating member; and
a partition wall separating the negative pressure generating member containing chamber and the liquid containing chamber and formed with the communicating portion; and
liquid ejecting means, receiving supply of the liquid from the liquid container, for performing printing,
wherein the liquid ejecting mechanism further comprises:
an atmospheric air introducing mechanism in the form of a recess provided in the partition wall on the side of the negative pressure generating member containing chamber, in communication with the communicating portion; and
a projecting portion, provided in a part of the atmospheric air introducing mechanism, projecting on the side of the negative pressure generating member containing chamber.
In the third aspect of the present invention, there is provided a liquid ejecting mechanism comprising:
a liquid container comprising:
a negative pressure generating member containing chamber housing a negative pressure generating member formed with fibrous material and having a liquid supply portion and an atmosphere communicating portion;
a liquid containing chamber forming a substantially enclosed space with a communicating portion communicated with the negative pressure generating member containing chamber and storing a liquid to be supplied to the negative pressure generating member; and
a partition wall separating the negative pressure generating member containing chamber and the liquid containing chamber and formed with the communicating portion;
liquid ejecting means, receiving supply of the liquid from the liquid. container, for performing printing, and
wherein the liquid ejecting mechanism further comprising:
an atmospheric air introducing mechanism communicating with the communicating portion and formed in the partition wall on the side of the negative pressure generating member containing chamber, the atmospheric air introducing mechanism including a recessed portion buffering pressure contact of the negative pressure generating member onto the partition wall and a projecting portion improving workability in assembling of the negative pressure generating member.
In the fourth aspect of the present invention, there is provided a liquid ejecting apparatus comprising:
a liquid ejecting mechanism having:
a liquid container including:
a negative pressure generating member containing chamber housing a negative pressure generating member formed with fibrous material and having a liquid supply portion and an atmosphere communicating portion;
a liquid containing chamber forming a substantially enclosed space with a communicating portion communicated with the negative pressure generating member containing chamber and storing a liquid to be supplied to the negative pressure generating member; and
a partition wall separating the negative pressure generating member containing chamber and the liquid containing chamber and formed with the communicating portion;
liquid ejecting means, receiving supply of the liquid from the liquid container, for performing printing,
a carriage mechanism to be scanned with carrying the liquid ejecting mechanism,
wherein the liquid container further comprising:
an atmospheric air introducing mechanism in the form of a recess communicating with the communicating portion and formed in the partition wall on the side of the negative pressure generating member containing chamber; and
a projecting portion provided in a part of the atmospheric air introducing mechanism and projecting on the side of the negative pressure generating member containing chamber.
In the fifth aspect of the present invention, there is provided a liquid ejecting apparatus comprising:
a liquid ejecting mechanism having:
a liquid container including:
a negative pressure generating member containing chamber housing a negative pressure generating member formed with fibrous material and having a liquid supply portion and an atmosphere communicating portion;
liquid containing chamber forming a substantially enclosed space with a communicating portion communicated with the negative pressure generating member containing chamber and storing a liquid to be supplied to the negative pressure generating member; and
a partition wall separating the negative pressure generating member containing chamber and the liquid containing chamber and formed with the communicating portion;
liquid ejecting means, receiving supply of the liquid from the liquid container, for performing printing,
a carriage mechanism to be scanned with carrying the liquid ejecting mechanism,
wherein the liquid container further comprising:
an atmospheric air introducing mechanism communicating with the communicating portion and formed in the partition wall on the side of the negative pressure generating member containing chamber, the atmospheric air introducing mechanism including a recessed portion buffering pressure contact of the negative pressure generating member onto the partition wall and a projecting portion improving workability in assembling the negative pressure generating member.
With the liquid container, the liquid ejection mechanism and the liquid ejection apparatus of the present invention constructed as set forth above, the upper portion of the atmospheric air introducing mechanism of the liquid container is formed into the buffer structure, and a projecting portion is provided as a part of the atmospheric air introducing mechanism so as to restrict increasing of :density of the portion contributing for gas/liquid exchange by the buffer structure, and also to restrict accumulation of a bubble by the projecting portion. At the same time, the projecting portion also serves as a guide structure for insertion into the receptacle chamber upon assembling of the negative pressure generating member. Furthermore, since the buffer structure is formed by providing the atmospheric air introducing groove at a position recessed from the surface of the partition wall, both sides of the negative pressure generating member are in contact with the surface of the partition wall, permitting a portion of the negative pressure generating member opposing to the atmospheric air introducing groove to freely expand, so that the atmospheric air introducing groove in the recessed position successfully prevents a large bubble from being formed with bubbles released from the negative pressure generating member being aggregated. On the other hand, the projecting portion at the lower portion acts for returning the portion of the negative pressure generating member once expanded upon insertion to the position near the height of the surface of the partition wall and for separating small bubbles from each other so as not to form a large bubble.
With the construction set forth above, abrupt increasing of density is hardly caused in the vicinity of the gas/liquid exchange groove or the atmospheric air introducing groove. Small bubbles released from the negative pressure generating member is unlikely to aggregate to form a large bubble to stablly flow into the liquid containing chamber with maintaining a small bubble state. Furthermore, in the assembling step of the liquid container, a stable negative pressure generating member insertion condition without curling up or floating can be obtained.
The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.